| 摘要 |
A swing hydraulic circuit in a construction machine, wherein no shock occurs when a swing member is started or stopped even if the reach of the working machine is small and no delay occurs when the swing member is started or stopped even if the reach of the working machine is large. For this purpose, the swinging hydraulic circuit is provided with a remote control valve (30) for swinging, which has its pilot pressure to the secondary side controlled by the operation of a lever; a directional control valve (4) changed over by the pilot pressure from the remote control valve (30) for swinging; a hydraulic motor (5) for swinging, which has its supply flow rate from a hydraulic pump (1) controlled by the directional control valve (4); and two relief valves (11a, 11b) provided in paths (6a, 6b) on both sides of a hydraulic motor (5) for swinging. The circuit is further provided with a set pressure control means capable of changing set pressures of the both relief valves (11a, 11b) in accordance with the attitude of the working machine. |
